Process for cracking hydrocarbons



May 22, 1928.

W. L. GOMORY PROCESS FOR CRACKNG HYDROCARBONS Feb. 14, 1920 ImferW@Awa-m HTlUPllL-fug,

Patented May 22, 1928.

UNITED STATES 1,670,804 vParleur OFFICE.I

WILLIAM L. GOMOBY, F CHICAGO, ILLINOIS, A SSIGNOR T0 CLIFFORD H.LEONARD, OF CHICAGO, ILLINOIS.

PROCESS FOB CBACKING HYDROCABBQNS.

Application led February 14, 1920. Serial No. 358,755.

My invention has for its object to provide a continuous process forcracking oil in which a large percentage of the li.ghter hydrocarbons isobtained with a mlnlmum development of carbon and fixed gases and inwhich the longevity of the apparatus 1s increased and the consumption offuel reduced to a minimum. With these and other objects in view, Icontinuously force a stream of oil or hydrocarbons through a coil heatedto a cracking temperature, injecting with the oil a suitable gas whichhas the `ei'ect of causing what carbon is developed to assume a porousfriable state in which it is readil driven out of the heating coil; thegas furt er assists in driving the carbon out of the coil; preferably Iemploy a gas rich in hydrogen for the purpose, which further acts toreduce the amount of carbon formed by combining with a portion thereofto form hydrocarbons. In my process moreover, the free carbon is at onceeliminated, thus increasing and minimizing the'. consumption of heat.

Other advantages of my invention will appear from the followmgspecification 1n which I have described a preferred form of apparatusand process; it is to be understood, however, that the s cie disclosureis for the purpose of exemp iiication only and that the scope of theinvention is defined in the following claims in which I have endeavoredto distinguish it from the prior art so far as known to me withouthowever relinquishing or abandoning any portion or feature thereof.

In the drawing accompan ing and forming a part of this application vhaveshown diagrammatically partly in section and partly in elevation anapparatus for carrying out my invention. The construction comprises afurnace 1 which may be of any suitable or approved type, through theheating chamber of which extends a coil of pipe 2 for heating petroleumorother heavy hydrocarbons to be cracked. Oil is supplied to the coilfrom a suitable tank or reservoir through a pipe 3 and is forced throughpipe 4 by pump 3'* and through to pipe 5 and into the upper end of coil2. A checkvalve 7 in p1pe 5 serves to prevent the return of the oil. Theoil in the coil of pipe 2 is maintained at a temperature of approximatel1000 Fahrenheit and the oil therein is maintained at a pressure whichmaybe in the effectiveness of the apparatusI the neighborhood of 150pounds, the temperature and pressure being such that 15 to 20 per centof the oil forced through the coil remains in the liquid phase. In orderto assist in the elimination of carbon, as above stated, I introducewith the oil a gas, which causes the carbon formed to be in a light,porous condition and which assists in carrying the carbon out of theheating coil, thus greatly increasing the longevity of the apparatusovercoming one of the greatest difficulties encountered in crackingprocesses. For this purpose a branch ipe 8 is connected through union10, chec -valve 11 and pipe 9 with a source of steam under pressure.Other inert gas may be employed instead of the steam. Preferably,however, I introduce a gas which is rich in available hydrogen, such ashydrogen gas er se, producer gas or the like. The hy rogen-containinggases have the advantage heretofore described in connection with theintroduction of neutral gases such as steam, together having a valve 13is connected to the union 10 for the introduction of suchhydrogencontaining gases.

It will be observed that the oil and gas are introduced at the upper endof the coil 2 and as the evolved gases tend to escape upward through thein-coming current of oil the uncondensable gases are largely re-absorbedin the oil. From the lower end of the heating coil the mixture of liquidoil, carbon, vapor and -ixed gases is conveyed by pipes 6, 14 to theexpansion tank 15 in which there is gravity separation, the heavyhydrocarbon containing the free carbon sinking to the bottom of the tankand the uncondensed vapors and gases rising to the top thereof. A gauge16 indicates the pressure. From the bottom of the tank the heavyhydrocarbons containingv free carbon are drawn off by pipe 17 into acooler 18 from which they are conducted to a tank or other storagereceptacle by pipe 19. Thus the carbon developed in the heating coil isat once removed from the system, and presents no obstacle to the furthercracking operation. The uncondensed portions of the mixportions thereofare condensed in tank 21 and return by pipes 22, 4, and 5 to the heatingcoil. As this oil contains practically no free carbon, its return to theheating coil'is unobjectionable. The fixed gases and the vaporsremaining uncondensed in tank 21 pass over by pipe 21"L to a condensingcoil 23 in which the vapors are condensed. Froml coil 23 the condensedvapors and fixed gases pass through the receiving tank 24 from which theliquid may be drawn oft' through valve 25. The receiving tank isprovided with a pressure gauge 26 and a pressure valve 27, the latterbeing for the purpose of releasing or carrying away the fixed gases asthe pressure rises above the desired point.

The rocess has been described in connection with the description of theapparatus, but may be briefiy stated as follows: Pressure is maintainedthroughout the s stem from the inlet of the heating coil to tiereceiving tank, slightly diminishing from the former to the latter but asufiicient pressure being maintained in the latter to maintain anydesired pressure of'say approximately 150 pounds in the heating coil.The temperature of the oil in the heating coil is raised ,to about 10000Fahrenheit, the precise temperature and pressure being determined by thefact that about 15 to 20 per cent of the oil is to be maintained in theliquid phase. The heat Within the coil results in the splitting up ofthe heavier hydrocarbons into lighter hydrocarbons with the depositionof carbon, the latter being deposited in porous, friable Aform becauseof the introduction of gas for that purpose, and when the gas introducedcontains a supply of hydrogen a certain part of the carbon is eliminatedby combination with hydrogen. At the same time that cracking takes placea considerable volume of non-condensable gas is developed which tends torise upward 1n the coil but is thereby brought into contact with, andabsorbed by the iii-coming stream of oil. The mixe-d products of theheat treatment are carried over into the expansion tank 15 where theyare separated by gravity, the heavier portions containing the fixedcarbon settling to the bottom and being drawn off through the coolingtank and then to storage. The portions or components which do notcondense in the tank 15 rise through the pipe 2O into tank 21 where theheavier ortions thereof are condensed and returned by pipes 22 and t tobe re-treated, it being noted that this component contains practicallyno free carbon and therefore introduces no new difficulty into thetreatment. The lighter vapors and fixed gases pass outward through pipe21 to condenser 23 where the vapors are condensed and flow with thegases into receiving tank 24, where the liquid is separated from thefixed gas. By separating the free carbon and heavy hydrocarbon andreturning only fractions of the oil practically free from the carbon,the life of the coil is increased since practically no carbon isreintroduced thereinto and, furthermore, the consumption of heat iscorrespondingly reduced.

I claim:

1. A process of cracking hydrocarbons consisting in forcing a mixturethereof with hydrogen through a conduit heated to a crackingtemperature, maintaining a pressure in said conduit such that aboutfifteen to twenty per cent of the hydrocarbons remain in the liquidphase at the temperature employed, drawing off the resulting liquid,vapors and gases, separating the liquid and condensing the vapors. o

2. The process of cracking hydrocarbons consisting in forcing a mixtureof the hydrocarbons and hydrogen through a conduit, heating the mixturetherein to a temperature of approximately 1000 degrees F., maintaining apressure in the conduit of approximately 150 pounds and therebyvaporizing between 80% and 85% of the mixture, drawing otf the resultantliquid, vapors and gases, separating the liquid and condensing thevapors.

3. A process of cracking hydrocarbons which consists in continuouslypassing a stream thereof downwardly through a heating conduit maintainedat a temperature of approximately 1000 degrees F. and then into a tank,maintaining a body of the liquid products from the cracking conduitquiescent in said tank, condensing the heavier portion of the vaporsescaping from said tank and mixing the condensate with the stream of oilflowing to the cracking conduit, separately condensing the lighterportion of the vapors and maintaining a pressure on the crackingconduit, tank and condenser-s sufcient to retain between 15%V and 20% ofthe oil in the crackingconduit in the liquid phase.

WILLIAM L. GOMORY.

